MODELING GREENHOUSE CROPS: STATE OF THE ART AND PERSPECTIVES

Crop modeling started in the early seventies with the elaboration of an integrated and dynamic vision of the whole plant physiology (de Wit, 1970) and with the generalisation of the use of computers in all scientific fields. It developed quickly as models appeared to be powerful scientific as well as engineering tools. Crop models offer a conceptual framework for the organisation of research: for their development, various persons or groups can mobilise their different skills in a co-operative project, and different levels of organisation can be co-ordinated. Models are also justified, generally by the same research teams, by their applicability for improving management of the system they describe. They usually provide quantitative information from which decisions, such as crop timing, irrigation, fertilisation, crop protection, and climate control, can be taken at the field scale. On a regional scale, policies can be evaluated from estimations of e.g. potential yield, water needs, or fertiliser losses.

In horticulture, a recent survey of the literature (Gary et al., 1998) shows that crop modelling significantly developed in the eighties. In greenhouse cultivation systems (for vegetable and ornamental production), it has been motivated by the need for quantitative information to improve decision making with the emerging computer tools that were designed to control the shoot and root environments. In these control systems, crop models can be used at the operational level to simulate the short-term crop processes that interact with the greenhouse climate (CO₂ and water vapour exchanges) and contribute to the daily crop growth (carbon balance). At the tactical level, models are needed to relate the general policy of climate control and crop management along the crop cycle to yield formation.

The major research teams in this field belong to regions of the world where the greenhouse industry is of economic importance and/or where crop modelling had already developed on other cultivation systems: the Netherlands, England, France, Israel, the USA, Germany, Sweeden, Canada… More recently, a modelling activity is emerging in regions where greenhouse cultivation is developing, like southern Europe (Portugal, Spain, Greece) and South America (Brazil, Colombia).

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